BIOMARKER RECORDS OF HYDROCLIMATE FROM THE PLIOCENE GREAT BASIN AND NORTH AMERICAN SOUTHWEST (Invited Presentation)

Models and theoretical predictions suggest that subtropical continents will dry as a result of anthropogenic warming, with impacts on water resources and ecosystems. However, geologic evidence from past warm periods like the Pliocene, just prior to the Pleistocene, document wetter conditions across the subtropics, at odds with theoretical expectations.In the Great Basin and North American southwest, evidence from the Pliocene suggests widespread lacustrine deposits and the presence of more mesic flora and fauna than are present on the landscape at present. In this talk, I show that compound-specific isotopic analyses of lipid biomarkers can provide a new perspective on the nature of Plio-Pleistocene hydroclimate changes in this region, presenting new data from lacustrine deposits in the Great Basin as well as data from marine sediment cores. In these settings, hydrogen isotopes in leaf waxes yield insights on Plio-Pleistocene changes in atmospheric circulation and the seasonality of precipitation. Interpreting these data in the context of model simulations and modern observational datasets reveals the processes responsible for Pliocene hydroclimate change, with direct application to understanding extreme precipitation in the 21^st century. From this perspective, the Pliocene and other past warm climates can generate key lessons for understanding and adapting to a warmer future.